This rifled gun was developed by the OKB-9 (now Spetstekhnika) design bureau in Sverdlovsk (now Ekaterinburg) in 1960 and was mounted on an experimental vehicle Ob'ekt 120 (chief designer G.S.Efimov). This gun stands out for its length and power and was originally envisioned as a maingun of a perspective heavy tank that never appeared.

This is probably the largest dedicated antitank gun ever built.

Some reports claim that this is the very project from which spawns the 152mm smoothbore gun that is carried by an elusive N.Tagil MBT.